Suede-like sheet material of an acrylic polymer containing an additive

ABSTRACT

AN IMPROVED SUPPLE, SYNTHETIC, MICROPOROUS VAPOR PERMEABLE SUEDE SHEET MATERIAL OF A NON-WOVEN SYTHETIC NEXIBLE FIROUS WEB THAT IS IMPREGNATED WITH A POLYMERIC BINDER OF AN ACRYLIC POLYMER AND ABOUT 0.1-20 PARTS OF ADDITIVE PER 100 PARTS OF POLYMER WHERE THE ADDITIVE IS EITHER A HYDROCARBON OIL, SILICONE OIL, ALKYL OLEATE, OR DIALKYL SEBACATE.

United States Patent 3,600,209 SUEDE-LIKE SHEET MATERIAL OF AN ACRYLIC POLYMER CONTAINING AN ADDITIVE Charles A. Young, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. No Drawing. Filed June 18, 1968, Ser. No. 737,826

Int. Cl. D06c 11/00; B44c N US. Cl. 1178 19 Claims ABSTRACT OF THE DISCLOSURE An improved supple, synthetic, microporous vapor permeable suede sheet material of a non-woven synthetic flexible fibrous web that is impregnated with a polymeric binder of an acrylic polymer and about 0.1-20 parts of additive per 100 parts of polymer where the additive is either a hydrocarbon oil, silicone oil, alkyl oleate, or dialkyl sebacate.

BACKGROUND OF THE INVENTION This invention relates to a novel suede-like microporous sheet material and in particular to a synthetic suede-like microporous vapor permeable sheet material that has a substantially improved nap over prior art synthetic suede products.

Leather-like sheet materials that can be formed into a suede-like sheet material have been prepared by a variety of processes as disclosed in the following patents: Graham et al. US. 2,715,588, issued Aug. 16, 1955; Gaylord U.S. 2,917,405, issued Dec. 15, 1959; Proctor U.S. 2,994,617, issued Aug. 1, 1961; Hollowell Pats. U.S. 3,067,482 and 3,067,483, both issued Dec. 11, 1962; British Pat. 986,437, published Mar. 17, 1965 and Fitz- Gerald et al. US. 3,228,786, issued Jan. 11, 1966. These sheet materials have a very wide variety of uses from shoe uppers to apparel suede. However, while these materials have been considered acceptable suede-like materials after bufiing, the surface of the material does not approach that of a natural leather suede as closely as is desired. The density and fiber length of the fibers that form the suede-like surface of these prior art products are insufficient to form a product which very closely resembles a natural leather suede.

A synthetic material that would closely resemble natural leather could be used as an apparel suede, a brushed casual shoe upper, as a felt-like mens hat material and the like.

The novel suede-like product of this invention surprisingly has a surface which more closely approaches that of natural suede leather than the aforementioned prior art products which are of a high quality and are excellent for many purposes. Along with this improved property, the novel product of this invention still is highly flexible, soft, supple and has a high Water vapor permeability. This is accomplished by using a particular additive with the polymeric binder used to form the sheet that will give a nap on the novel product with a high fiber density and a greater fiber length than previously has been possible with prior art products.

SUMMARY OF THE INVENTION The supple synthetic microporous vapor permeable suede sheet material comprises:

(a) a non-woven synthetic flexible fibrous web that is impregnated with (b) a polymeric binder which consists essentially of an acrylic polymer and contains 0.1-20 parts of a nap improving additive per 100 parts of polymeric binder which is either a hydrocarbon oil which consists essentially of parafiinic and naphthenic hydrocarbon constituents and has a Saybolt viscosity at 99 C. of 20- 200 seconds, a silicone oil which has a viscosity at 25 C. of at least 10 centistokes, an alkyl oleate where the alkyl group contains 4-30 carbon atoms or a dialkyl sebacate where the alkyl group contains 8-30 carbon atoms;

wherein said microporous sheet material has a water vapor permeability value of at least 1000 grams of water/ 100 square meters/hour and a binder to fiber ratio of about 0.2-3.0.

DESCRIPTION OF THE INVENTION The novel sheet material of this invention is prepared by forming a non-woven porous substrate or web, impregnating this web with a polymeric binder, and coagulating this polymeric binder, preferably into a microporous form. The non-woven web is impregnated with sufiicient polymeric binder to give the final product a binder/fiber ratio of about 0.2-3.0. For best results, a binder/ fiber ratio of 0.5-2 is preferred.

The term microporous refers to a porous material in which the individual pores are not discernible to the naked eye.

Preferably, the novel sheet material of this invention has a fiexural rigidity at a 50 mil sheet thickness of about LOGO-80,000 milligrams-centimeters, and more preferably, 4,00030,000 milligrams-centimeters, measured according to the method of ASTM-l388-D-64. A sheet having the flexural rigidity within the above ranges indicates that the sheet is supple and flexible and not stiff and board-like.

Water vapor permeability of the novel sheet material of this invention is determined by sealing the sheet on top of a cup containing CaCl This sealed cup is stored at relative humidity at 72 F. and the weight increase of the cup due to moisture permeating through the material is determined and the water vapor permeability value of the sheet is calculated in Grams of water square meters of material/ hour Preferably, the novel sheet material of this invention has a water vapor permeability of 2,000-15,000 grams/100 square meters/hour.

The non-woven porous fibrous substrate or web used to form the novel sheet material of this invention preferably has a density of about 0.01l.0 gram per cubic centimeter (gm./cc.), and more preferably, about 0.1-0.4 grn./cc. The method used to prepare the non-woven web and the fibers from which the web is prepared are not critical.

Generally, the non-Woven web is prepared by forming fibers into a loose batt by any known method, such as carding, blowing the fibers, dropping the fibers and the like. Preferably, a batt of about 4-20 ounces per square yard is formed by air-blowing the fibers. The batt is then compacted by any of the well-known techniques, such as mechanical needling. Preferably, the resulting web is further compacted by heat shrinking, for example, which can be accomplished by immersion in hot water. A web having properties of stretchability or shrinkability balanced in each direction is formed by cross-lapping the fibers into layers of dissimilar orientation within the plane of the web. When unidirectional stretchability or shrinkability is preferred, the crosslapping is omitted and most of the fibers are laid so that they have a similar orientation to the plane of the web.

The choice of the particular fibers from which the substrate used in this invention is made is not critical; for example, fibers of polyamides, polyesters, polyesterimides, polyurethanes, chain-extended polyurethanes, acrylic 3 polymers, acetate polymers, viscose rayon, glass and mixtures thereof, can be used. Elastomeric fibers can be used to form the web or can be blended with any of the aforementioned webs.

One particularly preferred non-woven substrate used to form the novel product of this invention which gives a high quality suede-like material is a non-woven web of needled, heat shrunk about l-2 denier polyethylene terephthalate fibers having a density of about 0.15-0.30 gm./cc.

A non-woven porous fibrous substrate that is impregnated with a polymeric material that has a binder to fiber ratio of less than 1.0 can also be used as a substrate to form the novel product of this invention. This substrate is reimpregnated with suflicient polymeric binder to give a product with a final binder/fiber ratio of less than 3, preferably 1-2. After impregnation, the polymer is coagulated in a microporous form. One preferred substrate of this type is a non-woven needled heat shrunk batt of polyethylene terephthalate fibers that has been impregnated with a mixture containing up to 50% by weight polyvinyl chloride and at least 50% by weight of a chain-extended polyurethane polymer. One preferred polyurethane is the reaction product of an aromatic diisocyanate and poly(alkyleneether) glycol which is chainextended with a dia'mine that has at least one active hydrogen attached to each nitrogen atom.

The acrylic polymeric binder used to impregnate the non-woven fibrous substrate to form. the novel sheet material of this invention should be tough and durable, and preferably, should form a microporous structure. These characteristics are necessary to form a product which is a suede leather replacement for shoe uppers, for wearing apparel, such as hats, coats, vests and the like. Acrylic polymers that form sheet materials that have these desired characteristics generally have a tensile stress at elongation of about 4-150 p.s.i., and preferably 8-72 p.s.i.

Tensile stress at 5% elongation is the force in pounds which is required to elongate a sample 5% divided by the cross-section area of the sample with the results being expressed in pound per square inch (p.s.i.). Preferably, an 8-12 mil thick film is prepared from the acrylic polymer used to prepare the novel sheet material of this invention. Test samples of about /2 inch by 4 inches are cut, conditioned at 50% relative humidity and tested at 23 C. The samples are tested at the above temperature and humidity conditions on an Instron Tensile Tester using about 1 inch between grips on the sample, a cross-head speed of 1 inch per minute and a chart speed of 10 inches per minute.

The acrylic polymeric binder used for the novel sheet material of this invention is an acrylic polymer which consist essentially of a lower alkyl acrylate or a lower alkyl methacrylate, where the alkyl group contains from 1-8 carbon atoms, a second copolymerizable constituent, and an oz,}3 ethylenically unsaturated wrboxylic acid such as methacrylic acid, acrylic acid, itaconic acid and the like.

Typical lower alkyl methacrylate useful in forming the acrylic polymer used to form the novel sheet material of this invention are methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate, hydroxy butyl methacrylate and the like. Typical lower alkyl acrylates are for example, ethyl acrylate, butyl acrylate and ethyl hexyl acrylate, hydroxy ethyl acrylate, hydroxy propyl acrylate, hydroxy butyl acrylate and the like. Preferably, for a high quality product an alkyl group and/ or an alkyl acrylate ester is used having 2-8 carbon atoms in the alkyl group.

The second copolymerizable constituent of the acrylic polymer used in this invention can be, of course, any of the aforementioned methacrylate or acrylate esters, styrene, vinyl toluene, acrylonitrile, methacrylonitrile, vinylacetate, vinylchloride, acrylarnide, methacrylamide and the like.

One particularly preferred acrylic polymer which forms a high quality suede-like product of this invention is a terpolymer of about 40-60% by weight 2-ethylhexyl acrylate, 30-60% by weight methyl methacrylate and 2-8% by weight methacrylic acid. Another preferred acrylic polymer used to prepare the novel sheet material of this invention is a polymer of 60-70% 'by weight ethylacrylate, 30-70% by weight methylmethacrylate, 1-4% by weight methacrylic acid and 3-5% by weight methacrylamide. Another useful terpolymer comprises -90% by weight ethyl acrylate, 5-15% by weight styrene and 1-8% by weight methacrylic acid.

The above acrylic polymeric binder can be in. a solution or a dispersion to impregnate the non-woven substrate to form the novel sheet material of this invention. Preferably, dispersions of the above polymer either using an organic or an aqueous phase as the dispersing medium are used to impregnate the non-Woven substrate to form the novel sheet material of this invention. Dispersions can readily be formed that contain a high polymer solids content 'but have a low viscosity and are readily adaptable to an impregnation process Aqueous dispersions or latices of the above acrylic polymeric binders are particularly preferred since there are no problems such as occur with solvent dispersions, such as the high cost of solvents which require solvent recovery. Moreover, latices are readily coagulated after impregnating the non-woven substrate by heat or cold or by chemicals into a microporous structure.

Preferably, for best results, the latex of the acrylic polymeric binder used in this invention has a low viscosity of 1-300 centipoises and a polymer solids content of about 20-70% by weight and more preferably, a 40- 60% polymer solids content is used.

To give a novel suede-like sheet material of this invention a dense nap with long fibers, an additive of a hydrocarbon oil, silicone oil, alkyl oleate, or a dialkyl sebacate is added to the polymeric binder in an amount of 0.1-20 parts of additive per parts of polymeric binder. For best results, about 5-15 parts of additive per 100 parts of binder are used.

The hydrocarbon oil used as an additive in this invention is a petroleum oil fraction which consists essentially of parafinic and naphthenic hydrocarbon constituents and has a Saybolt viscosity of 99 C. of 20-200 seconds. Preferred hydrocarbon oils are the white non-staining oils which have a Saybolt viscosity at 99 C. of 40-90 seconds. These preferred hydrocarbon oils typically contain about 40-100% by weight of a parafiinic constituent and 600% by weight of a naphthenic constituent. Since these oils are petroleum fractions, they generally contain other constituents which may be aromatic or aliphatic in character. One particularly preferred oil contains about 43- 47% by weight of a paraffinic constituent, 38-42% by weight of a naphthenic constituent and 13-17% by weight of an aromatic constituent and has a Saybolt viscosity at 99 C. of about 52-56 seconds.

The silicone oils that are useful additives in this invention are of the formula where R is an alkyl group of 1-4 carbon atoms or a phenyl group or a mixture of alkyl and phenyl groups, and the oil has a kinematic viscosity at 25 C. of at least 10 centistokes and may have a viscosity up to 2.5 x10 centistokes. Preferably, the oil has a kinematic viscosity of 50-30,000 centistokes. The aforementioned R group can be methyl, ethyl, propyl, isopropyl butyl, isobutyl or phenyl. One preferred silicone oil, since it gives a high quality product, is polydimethylsiloxane which has a kinematic viscosity at 25 C. of about 20-100 centistokes.

The alkyl oleate additive used in this invention contains 4-30 carbon atoms in the alkyl group and are, for example, butyl oleate, hexyl oleate, octyl oleate, cetyl oleate, lauryl oleate, tridecyl oleate and the like. Butyl oleate is one preferred additive of this group since it provides a product with a long dense nap.

The dialkyl sebacate additive used in this invention contains 8-30 carbon atoms in the alkyl group and are, for example, dioctyl sebacate, dicetyl sebacate, dilauryl sebacate, ditridecyl sebacate and the like. Dioctyl sebacate is particularly useful in this invention since it forms a suede-like product which has a dense nap with long fibers.

Often it is desirable to add pigments, extender pigments and dyes to the latices used to form the novel sheet material of this invention to give the product the desired color. About 01-20% by weight pigment, based on the Weight of the polymer in the latex, and preferably, 2-10% by weight can be used. Typically useful pigments are, for example, metal oxides, such as titanium dioxide, zinc oxide, metal hydroxides, chromates, silicates, sulfides, sulfates, carbonates, carbon blacks, organic dyes, such as .B-copper phthalocyanine, lakes and metal flake pigments, ferric yellow (yellow iron oxide pigment), burnt sienna (an orange brown mineral pigment containing iron oxide, manganese dioxide and clay), and the like.

Thickening agents can be added to the latex used in this invention to give the desirable impregnating viscosity. The useful viscosity range for the latices used to form the novel sheet material of this invention is about 1 to 300 centiposes (cps) with the preferred range being about to 100 (cps). Thickening agents most commonly used are ammonium caseinate, ammonium alginate, methyl cellulose cps. to 50,000 cps. viscosity, measured as a 2% aqueous solution at 25 C.) and sodium polyacrylate. Other thickening agents, such as polyacrylic acids, polyvinyl alcohol, carboxyrnethyl cellulose, polyvinyl pyrrolidone, maleic acid copolymers, gelatine, and the like, can also be used. It is desirable, but not absolutely necessary, to remove the thickener from the latex after it has been coagulated; this is accomplished by washing the coagulated latex with water. If the thickener is retained in the sheet, subsequent rewetting of the material causes the thickener to come to the surface and makes the material feel slimy. This washing step may be eliminated from the process by crosslinking and insolubilizing the thickener and can be accomplished by adding a cross-linking agent such as polyacrylamide and an agent which insolubilizes the thickener, such as hishydroxymethyl urea. The subsequent drying and curing of the polymer after coagulation at an elevated temperature aids in the crosslinking and insolubilization of the thickener.

Antioxidants may be added in small amounts to the latex used in this invention particularly if ethylenically unsaturated monomers are used the acrylic polymers, such as 4,4' butylidene-bis-(6-tertiary-butyl-m-cresol), 2,2- methylene bis (4 methyl 6 tertiary butylphenol), 4,4-thio-bis-(6-tertiary-butyl-m-cresol) and the like.

Plasticizers may be added in small amounts to the latex to form the novel sheet material of this invention. The type of plasticizer used is dependent on the latex polymer. Phthalate esters, such as benzyl butyl phthalate, are particularly useful for the acrylic polymers used in this invention.

Curing agents may be added in small amounts to the latex used to form the novel sheet material of this invention, such as zinc oxide; ammonium salt, such as ammonium chloride; melamine-formaldehyde polymers; phenolformaldehyde polymer. Curing or vulcanization of the latex polymer after it is coagulated in the non-woven substrate is carried out at about 100160 C. and preferably, at 110-150" C.

If the latex is coagulated by heat, generally heat sensitizers, such as polyvinylmethylether, ammonium sulfate, zinc ammonium acetate, methylcellulose and the like, are added. Heat coagulation can be accomplished by hot air, steam, microwave, infrared heat and the like. A temperature of about 40-100 C. is usually required with the preferred temperature range being about 60-90 C.

If the latex is coagulated by chemical means, the impregnated sheet is immersed in a liquid, for example, an acetic acid bath containing about 1 to 10% by weight acid. Solutions of the following can be used to coagulate the latex: calcium chloride, barium chloride, zinc acetate, formic acid, aluminum sulfate and the like.

Preferably, after the non-woven web is impregnated with the latex, the latex is coagulated by freezing the latex at about 20 C. to -l00 C. for about 10 minutes to 2 hours. After coagulation, the novel sheet material is dried, preferably at a temperature of about 30-l50 C. However, it is possible to dry the product at a lower temperature, for example, room temperature about 22 C.

If a colored product is desired, the novel sheet material of this invention can be dyed by ordinary techniques after the polymer has been coagulated. Manwaring US. Pat. 3,337,289, issued Aug. 22, 1967, teaches a dyeing process that can be used on the novel product of this invention. Preferably, the non-woven web is dyed and then a colored polymeric binder is used to form the novel sheet material of this invention. The binder is colored as aforementioned by the addition of dyes or pigments.

Printing, stencilling, embossing, preferential dyeing, and other known techniques for surface decoration can be used to modify the novel product of this invention.

When a denser product is wanted, the dried sheet is pressed between two smooth heated surfaces. The time, temperature and pressure of pressing are controlled to maintain product permeability and suppleness, as will be apparent to those skilled in the art.

The suede surface of the novel sheet material of this invention is formed by raising a nap on one or both sides of the smooth, supple microporous sheet in any suitable manner known in the art of napping fabrics and tanned skins. A preferred napping process involves bufling with emery covered rolls followed by brushing. Bufiing also improved the suppleness of the product besides softening its surface feel.

Another optional feature is to treat the novel product with known fabric softeners, or to likewise treat the mat at any stage of the process.

In general, the product of this invention is a versatile material with many uses. The novel product of this invention, because of its desirable properties, may be buffed on one side and coated on the other, for example, coated with a microporous layer.

The following examples illustrate the invention. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 The following ingredients are blended together to form latex binder A:

Parts by wt. Acrylic latex-45% polymer solids dispersion of terpolymer of ethyl acrylate/methyl methacrylate/methacrylic acid in weight ratio of 64/ 32/4 200.0 Ammonia solution-14% by Weight aqueous solution 1.4 Zinc oxide dispersion-50% zinc oxide solids 10.0 Lampblack dispersion50% solids 4.0 Primol D emulsion-50% aqueous emulsion of a mineral oil that has naphthenic and parafinnic constituents and has a Saybolt viscosity at 99 C.

of 54 seconds 20.0 Nonionic surfactant solution-25% aqueous solution of Triton X-100 which is the condensation product of octyl phenol and 9-10 moles of ethylene oxide 12.0 Ammonium sulfate solution-40% aqueous solution 30 0 The tensile stress at elongation of a dried coalesced non-porous film of the above latex is greater than 4 p.s.i., determined at 23 C. and 50% RH. on a 0.5 inch wide sample of an Instron tensile tester using 1 inch between jaws and an elongation rate of 1 inch per minute.

An 18 inch by 18 inch by inch Web prepared by needling and heat shrinking a batt of 1.8 denier polyethylene terephthalate fibers 1.5 inches in length and having a density of about 0.22 gram/ cubic centimeters is immersed in the above prepared latex binder. The amount of latex binder picked up by the web is about 350% by weight. This impregnated web is placed between two aluminum sheets and this assembly is placed in an oven, heated to about 80 C. and held at this temperature for 30 minutes to coagulate the latex binder. The web is then washed with warm water and dried for one hour in a circulating air oven held at about 100 C. The sheet is then split and buffed on both sides with 120 grit sandpaper removing about 3 mils of material from each side. The resulting suede-like material is a soft, supple and flexible substrate.

Latex B is formulated using the identical ingredients and in the same amounts as used to formulate latex A, except mineral oil emulsion is omitted. The resulting latex polymer has a tensile stress at 5% elongation greater than 4 p.s.i., determined as indicated above. A non-woven web of polyethylene terephthalate fibers as described above is impregnated with latex B using the same precedure as above. The impregnated web is split and buffed using the identical procedure shown above.

The resulting sheet materials formed from latex A and a latex B have the following physical properties:

Latex A Latex B Mineral oil (parts of oil per 100 parts of polymer) 0 Binder/fiber ratio 1. 14 1. 38 Thickness (mils) 50 58 Density of the impregnated web (g 0. 57 0.60 Nap length (mils) 30 8*30 Nap density High Low No'ru.-M/T: machine direction/transverse direction.

EXAMPLE 2 A latex binder C is formed as in Example 1 using the same ingredients except a 50% by weight emulsion of n-butyl oleate is substituted for the mineral oil emulsion used in Example 1. A suede-like sheet material is then prepared using the same non-woven web and the same procedure of Example 1.

The resulting suede-like material is a soft, supple, flexible substance that has the following physical properties:

Binder/fiber ratio-1.40

Thickness-61 mils Density of impregnated web0.56 g./cc.

Water vapor permeability-10,000 g./ 100 m. /hr. Tensile strength at break (M/T)-l100/680 p.s.i. Percent elongation at break (M/T)--190/230 Nap length45 mils Nap densityhigh (M/TMachine direction/transverse direction) The tensile strength and percent elongation at break of the substrate are determined at 23 C. and 50% RH. on a 0.5 inch wide sample by an Instron tensile tester using 1 inch between jaws and an elongation rate of the sample of about 1 inch per minute.

Nap density-low nap density indicates relatively few fibers protruding from buffed surface, a high nap density indicates that the surface is completely covered with nap, a medium nap density is acceptable but does not have as great a fiber density as does the high density product.

The resulting sheet material has an excellent suedelike surface, excellent tactile characteristics and an appearance similar to that of natural suede leather.

EXAMPLE 3 A latex binder D is formed as in Example 1 using the same ingredients except a 50% by weight emulsion of dioctyl sebacate is substituted for the mineral oil emulsion used in Example 1. A suede-like sheet material is then prepared using the same non-woven web and the same procedure of Example 1.

The resulting suede-like material is a soft supple, flexible substrate that has qualities of a natural leather suede that has the following physical properties:

Binder/fiber ratio-1.42

Thickness-63 mils Density of impregnated web0.58 g./ cc. Water vapor permeability8840 g./100 mP/hr. Tensile strength at break (M/T)-l090/770 Percent elongation at break (M/T)180/250 Nap length-12-35 mils Nap densityMedium EXAMPLE 4 The following ingredients are blended together to form latex binder E:

Parts by weight Acrylic latex (46% polymer solids dispersion of a terpolymer of Z-ethylhexyl acrylate/methyl methacrylate/methacrylic acid in a weight ratio of 54/44/2) (latex pH:9.2) 217.5 Zinc oxide dispersion-50% zinc oxide 10.0 Primol D emulsiondescribed in Example 1 30.0 Aqueous lampblack dispersion-50% solids 4.0 Aqueous solution containing 10% by weight of acetic acid and 10% by weight of the sodium salt of sulfate methyl oleate 21.4

Total 282.9

An 18 inch by 18 inch by 0.2 inch web described in Example 1 is immersed in the above prepared latex and passed between two rolls to yield a 325% pick-up by weight of latex binder. The impregnated Web is placed between two aluminum plates 0.125 inch thick, and the assembly is immersed in pulverized Dry Ice for 30 minutes to coagulate the latex binder. The web is then thawed, washed with water and dried during minutes in a circulating air oven held at about C. The product is split and buffed on both sides with grit emery paper removing about 5 mils material from each side.

Latex F is formulated with the identical ingredients and amounts as used to formulate Latex E except that the mineral oil emulsion is omitted. A non-woven web described in Example 1 is impregnated with this latex, the latex is coagulated, and the product is washed, dried, split and buffed as described above.

The resulting sheets of buffed material have the followmg properties:

NoTE.-M/T: machine direction/transverse direetion.

The above results indicate that the mineral oil additive greatly improves the length and density of the nap with out adversely affecting other properties of the sheet.

9 EXAMPLE A heat shrunk non-woven web of needled polyethylene terephthalate fibers is impregnated with a chain-extended polyurethane solution described in Example 1 of Holden US. 3,100,321, issued Aug. 13, 1963, to forma microporous sheet material that is split to a thickness of about 70 mils. This sheet has a binder/fiber ratio of about 0.5 and a density of about 0.35 g./cc.

The above microporous sheet material is reimpregnated with a latex binder having the following composition:

Total 1575 Excess latex binder is squeezed from the sheet by a pair of nip rolls. The resulting product is dried at 110 C. Both sides of the sheet are bulfed with 120 grit sandpaper, yielding an attractive suede-like material useful, for example, for shoe uppers.

This final product is a suede-like material and is soft, supple and flexible and has the following properties:

Thickness61 mils Binder/fiber ratio-l.l4

Density0.47 g./ cc.

Water vapor permeability9,400 g./100m. /hr. Tensile strength at break (M/T)-l550/ 1030 p.s.i. Elongation at break, (M/T)150/ 180% Nap length6-40 mils Nap densityMedium (M/T)machine direction/transverse direction EXAMPLE 6 Latex G is formulated by using the identical ingredients and in the same amounts as used to formulate latex A except that 50 grams of the following silicone oil dispersion is substituted for the mineral oil dispersion used in latex A: 10% aqueous emulsion of silicone compound Dow Corning Antifoam B which is believed to be a thickened dimethyl siloxane oil that has a viscosity at 25 C. of at least 20 centistokes. A non-woven web of polyethylene terephthalate fibers identical to the Web described in Example 1 is impregnated with latex G, the latex is coagulated and the web is split and buifed as in Example 1.

The resulting sheet material has an excellent suedelike surface, excellent tactile characteristics and an appearance similar to that of natural suede leather.

What is claimed is:

1. A supple synthetic microporous vapor permeable suede-like sheet material consisting essentially of (a) a non-woven synthetic flexible fibrous web impregnated with (b) a polymeric binder which consists essentially of an acrylic polymer and contains a nap improving additive about 0.1-20 parts of additive per 100 parts of polymeric binder selected from the group consisting of a hydrocarbon oil which consists essentially of naphthenic and parafiinic hydrocarbon constituents and has a Saybolt viscosity at 99 C. of 20-200 seconds, a silicone oil which has a kinematic viscosity at 25 C. of at least 10 centistokes, an alkyl oleate where the alkyl group contains 4-30 carbon atoms or a dialkyl sebacate in which the alkyl group contains 8-30 carbon atoms;

10 said microporous sheet material having at least one suede surface, a water vapor permeability of at least 1000 grams/ square meters of sheet material/hour and a binder/ fiber ratio of 0.2-3.0.

2. Microporous suede-like sheet material of claim 1 in which the binder contains l-lS parts of additive per 100 parts of polymer, the water vapor permeability is about 2,000-15,000 grams/100 square meters/hours, and the binder/fiber ratio is about 0.5-2.

3. The microporous suede-like sheet material of claim 2 in which the polymeric binder is a terpolymer of lower alkyl acrylate, said alkyl group having 2-8 carbon atoms, a lower alkyl methacrylate, said alkyl group having 1-4 carbon atoms, and an afi-ethylenically unsaturated monocarboxylic acid.

4. The microporous suede-like sheet material of claim 3 in which the polymeric binder is a terpolymer of ethyl acrylate, methyl methacrylate and methacrylic acid.

5. The microporous suede-like sheet material of claim 3 in which the polymeric binder is a terpolymer of 2- ethylhexyl acrylate, methyl methacrylate and methacrylic acid.

6. The' microporous suede-like sheet material of claim 2 in which the acrylic polymer consists essentially of a lower alkyl acrylate, said alkyl group having 2-8 carbon atoms, styrene and an a,fl-ethylenically unsaturated monocarboxylic acid selected from the group consisting of methacrylic acid and acrylic acid.

7. The microporous suede-like sheet material of claim- 3 in which the additive is a hydrocarbon oil which consists essentially of 40-100% by Weight of a paraffinic constituent and 60-0% by Weight of a naphthenic constituent and has a Saybolt viscosity at 99 C. of 40-90 seconds.

8. The microporous suede-like sheet material of claim 3 in which the additive is a silicone oil of the formula L M- J n where R is selected from the group consisting of an alkyl group having 1-4 carbon atoms and a phenyl group and said silicone oil has a kinematic viscosity at 25 C. of about 50-30,000 centistokes.

9. The microporous suede-like sheet material of claim 3 in which the additive is an alkyl oleate where the alkyl group contains 4-3() carbon atoms.

10. The microporous suede-like sheet material of claim 3 in which the additive is dialkyl sebacate where the alkyl group contains 8-30 carbon atoms.

11. The microporous suede-like sheet material of claim 3 in which said non-woven web consists essentially of polyethylene terephthalate fibers.

12. The microporous suede-like sheet material of claim 11 in which the additive is a hydrocarbon oil which consists essentially of 40-100% by weight of a paraffinic constituent and 60-0% by weight of a naphthenic constituent and has a Saybolt viscosity at 99 C. of 40-90 seconds.

13. The microporous suede-like sheet material of claim 11 in which the additive is a silicone oil of the formula LS1 l L (CH3); 0 n and has a kinematic viscosity at 25 C. of about 20-100 centistokes.

14. The micorporous suede-like sheet material of claim 11 in which the additive is butyl oleate.

15. The microporous suede-like sheet material of claim 11 in which the additive is dioctyl sebacate.

16. The microporous suede-like sheet material of claim 1 in which the non-woven synthetic flexible fibrous web before being impregnated contains an impregnant of a polymeric material and has a binder/fiber ratio of less than 1.

17. The microporous suede-like sheet material of claim 16 in which the impregnant of the polymeric material consists essentially of at least 50% by'weight of a chain-extended polyurethane and up to 50% by weight of polyvinyl chloride.

18. A process for forming a supple synthetic microporous vapor permeable suede-like sheet material which comprises (a) impregnating a non-woven fibrous web with (b) a polymeric binder which consists essentially of an acrylic polymer and contains a nap improving additive about 01-20 parts of additive per 100 parts of polymeric binder selected from the group consisting of a hydrocarbon oil which consists essentially of naphthenic and paraffinic hydrocarbon constituents and has a Saybolt viscosity at 99 C. of 20-200 seconds or a silicone oil which has a kinematic viscosity at 25 C. of at least centistokes; an alkyl oleate where the alkyl group contains 4-30 carbon atoms or a dialkyl sebacate in which the alkyl group contains 8-30 carbon atoms;

(c) removing excess liquid from the web and drying the web; and

(d) napping at least one side of the impregnated web to form a suede-like surface;

said microporus sheet material having a water vapor permeability of at least 1000 grams/100 square meters of sheet material/hour and a binder/fiber ratio of 0.2-3.0.

19. A process for forming a supple synthetic microporous vapor permeable suede-like sheet material which comprises the following steps.

(a) forming a microporous sheet having a binder/ fiber ratio of less than 1 by impregnating a nonwoven synthetic fibrous flexible web with a polymeric binder, coagulating said binder and washing and drying said sheet;

(b) reimpregnating the microporous sheet formed in synthetic flexible step (a) above with a latex of a polymeric binder which consists essentially of an acrylic polymer and contains a nap improving additive about 01-20 parts of additive per 100 parts of polymeric binder selected from the group consisting of a hydrocarbon oil which consists essentially of naphthenic and paraffinic hydrocarbon constituents and has a Saybolt viscosity at 99 C. of 20-200 seconds, a silicone oil which has a kinematic viscosity at C. of at least 10 centistokes; an alkyl oleate where the alkyl group contains 4-30 carbon atoms a dialkyl sebacate in which the alkyl group contains 8-30 carbon atoms; coagulating the latex and washing and drying said sheet material; and

(c) napping at least one side of the reimpregnated web to form a suede-like surface;

the resulting sheet material having a water vapor permeability of at least 1000 grams/100 square meters of sheet material/hour and a binder/fiber ratio of 0.2-3.0.

References Cited UNITED STATES PATENTS 2,715,588 8/1955 Graham et a1. 162135 2,993,811 7/1961 Smith et a1. 117139.5 3,067,482 11/1962 Hollowell 2874 3,167,448 1/1965 Hirshfeld 117-138.8 3,400,013 9/1968 Harrison 117140X ALFRED L. LEAVITT, Primary Examiner E. G. WHITBY, Assistant Examiner US. Cl. X.R. 

